Donnerstag, 21. September 2017 - 08:45 Uhr

OSIRIS-REx will fly by Earth on Sept. 22 to use our planet's gravity to propel the spacecraft onto Bennu's orbital plane. As of Friday, Aug. 25, the spacecraft is about 10.3 million miles (16.6 million kilometers) from Earth.

NASA's OSIRIS-REx spacecraft fired its thrusters to position itself on the correct course for its upcoming Earth flyby. The spacecraft, which is on a two-year outbound journey to asteroid Bennu, successfully performed a precision course adjustment on Wednesday to prepare for the gravity slingshot on Sept. 22.

This trajectory correction maneuver was the first to use the spacecraft's Attitude Control System, or ACS, thrusters in a turn-burn-turn sequence. In this type of sequence, OSIRIS-REx's momentum wheels turn the spacecraft to point the ACS thrusters toward the desired direction for the burn, and the thrusters fire.

After the burn, the momentum wheels turn the spacecraft back to its previous orientation. The total thrust is monitored by an on-board accelerometer that will stop the maneuver once the desired thrust is achieved.

High-precision changes in velocity, or speed and direction, will be critical when the OSIRIS-REx spacecraft operates near Bennu. Because Bennu is so small, it has only a weak gravity field. Therefore, it will only require tiny changes in velocity to do many of the maneuvers that are planned to explore and map the asteroid.

The Aug. 23 maneuver began at 1 p.m. EDT and lasted for approximately one minute and 17 seconds. Preliminary tracking data indicate that the maneuver was successful, changing the velocity of the spacecraft by 1.07 miles per hour (47.9 centimeters per second) and using approximately 16 ounces (0.46 kilogram) of fuel.

OSIRIS-REx will fly by Earth on Sept. 22 to use our planet's gravity to propel the spacecraft onto Bennu's orbital plane. As of Friday, Aug. 25, the spacecraft is about 10.3 million miles (16.6 million kilometers) from Earth.

The mission team has another minor Earth-targeting maneuver tentatively planned for Sept. 12. Over the next few weeks, the navigation team will process daily spacecraft tracking data from Wednesday's maneuver to determine whether the additional maneuver is necessary before the Earth gravity assist.

This fall, NASA’s asteroid-hunting spacecraft, OSIRIS-REx, will fly by Earth and use the planet’s gravitational force to slingshot itself out into space. This maneuver, known as an Earth Gravity Assist, will put OSIRIS-REx on course to visit asteroid Bennu, where it will collect a sample of some of the oldest material in the solar system. While the engineering team is busy carrying out the Earth Gravity Assist, the mission invites members the public to mark the occasion by participating in the Wave to OSIRIS-REx social media campaign.

HOW TO JOIN:

Take a picture of yourself or your group waving to OSIRIS-REx as it approaches Earth. Then share your photo using the hashtag #HelloOSIRISREx and tagging the mission account on Twitter (@OSIRISREx) or Instagram (@OSIRIS_REx). Bonus: Download these printable graphics to include in your photo.

WHEN:

Start posting pictures as soon as you like, or wait until the OSIRIS-REx spacecraft makes its closest approach to Earth at 16:52 UTC/12:52 ET/9:52 PT on Friday, Sept. 22, 2017.

WHO:

People all over the world! Science centers, air and space museums, K-12 classes, universities and other groups are also encouraged to gather a crowd for a photo during the spacecraft’s flyby on Sept. 22. Planning a group photo at your facility? Let us know. Contact us at socialmedia@orex.lpl.arizona.edu.

The OSIRIS-REx mission, NASA and other mission-related accounts may re-share some submissions on social media, create a mosaic or other combined products, or aggregate selected submissions on relevant websites.

Quelle: NASA

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Update: 10.09.2017

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‘Sling-shot’ show for NASA spacecraft over Australia

Stargazers will be treated to a rare skyshow when NASA’s OSIRIS-REx spacecraft ‘sling-shots’ its way over Australian skies on September 23.

Using Earth’s gravity to give it an orbital boost, OSIRIS-REx will rendezvous with the asteroid Bennu in 2018. The Earth flyby will give astronomers and those with high-end cameras a chance to view this rare encounter.

OSIRIS-REx is on an extraordinary journey to bring back to Earth a sample from the surface of the carbonaceous asteroid Bennu that could potentially record the early history of the solar system and molecular precursors to the origin of life.

The ‘sling-shot’ or Earth Gravity Assist manoeuvre will bring OSIRIS-REx close enough to Earth to be viewed through high-end cameras, where Desert Fireball Network (DFN) team members will be stationed across Australia in strategic locations to optimise viewing angles, creating a 3D triangulated track above Australia and demonstrating the capabilities of the DFN system.

Curtin University Professor Phil Bland, team leader of the Desert Fireball Network, and member of the OSIRIS-REx science team, said the rare encounter would offer an opportunity to highlight the capabilities of the DFN and planetary science research in Australia.

“The teams will be equipped with high-end DSLR cameras that will work together to track the OSIRIS-REx spacecraft across the sky from each viewpoint, enabling the DFN team to create a 3D triangulated track of its sling-shot around the Earth,” Professor Bland said.

“This important milestone furthers the work of planetary research here at Curtin and our relationship with NASA.

“We know very little about how the planets came together and why the Earth has the composition that it does. The samples that OSIRIS-REx delivers may hold the key to some of these answers.”

The DFN project is based at Curtin University in Perth, Western Australia, and aims to unlock the mysteries of our universe by studying meteorites, fireballs and their pre-Earth orbits.

Together with NASA, the DFN is expanding to a Global Fireball Observatory through the Solar System Exploration Research Virtual Institute (SSERVI). SSERVI’s science and technical research focuses on the connection between planetary exploration and human exploration via funded US teams and a large network of international partners.

The apparent pathway of the OSIRIS-REx spacecraft over Australian skies will take an hour, beginning over Rockhampton at 00.22am (AEST) and exit over Adelaide at 00.53am local time on September 23.

Quelle: Curtin University

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Update: 11.09.2017

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Large Binocular Telescope Snags First Glimpse of NASA’s OSIRIS-REx Spacecraft Since Launch

This set of magnified, cropped images shows NASA’s OSIRIS-REx spacecraft (highlighted in red) as it approaches Earth for its Sept. 22 Earth Gravity Assist. To improve visibility, the images have been inverted so that black and white are reversed. The images were taken Sept. 2, by the Large Binocular Telescope Observatory located on Mount Graham in Arizona. This is the first Earth-based view of the spacecraft since its launch on Sept. 8, 2016.

OSIRIS-REx, which was approximately 7 million miles (12 million kilometers) away when the images were taken, appears at approximately 25th magnitude.

The Large Binocular Telescope is a pair of 8.4-meter mirrors mounted side by side on the same mount, that can work together to provide resolution equivalent to a 22.7-meter telescope. The telescope typically conducts imaging of more distant objects but took this opportunity to look for OSIRIS-REx with a pair of wide-field cameras (one per mirror) as the spacecraft approaches Earth for its gravity assist. This encounter will change the spacecraft’s trajectory and set it on course to rendezvous with asteroid Bennu, where it will collect a sample of surface material and return it to Earth for study in 2023. The Large Binocular Telescope Observatory is headquartered on the Tucson campus of the University of Arizona.

The OSIRIS-REx mission team is collecting other images of the spacecraft taken by observatories and other ground-based telescopes around the world during this period – approximately Sept. 10-23, depending on location and local conditions. Individuals and groups may submit images of the spacecraft via the mission’s website, where instructions to locate the spacecraft in the sky are also available.

Quelle: NASA

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Update: 13.09.2017

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Skygazers prepare for OSIRIS-REx to swoop past Earth

As NASA’s asteroid-sampling spacecraft approaches Earth for a gravity boost, astronomers turn their eyes to the heavens. Stuart Gary reports.

Stargazers will have a chance to get a close-up look at NASA’s OSIRIS-REx spacecraft when the three-metre-wide probe sweeps through Earth’s skies for a close approach above Australia during the early morning hours of September 23, 2017.

The spacecraft is undertaking a gravity-assist slingshot manoeuvre, designed to build up speed and modify its trajectory to eventually intercept 101955 Bennu, an asteroid half a kilometre across which has a 1-in-2700 chance of hitting the Earth in the next 200 years.

That’s the third-highest rating on the Palermo Technical Impact Hazard Scale – a logarithmic rate used by astronomers to determine the potential impact hazard of a near-Earth object (or NEO) based on the probability of an impact and the estimated damage likely to be caused.

OSIRIS-REx's journey from the lab to asteroid Bennu

OSIRIS-REx will inspect Bennu in great detail, examining its orbit and composition, and collecting samples for return to Earth.

A key focus of the mission will involve studying the “Yarkovsky effect” caused by sunlight heating the surface of the asteroid.

That heat is eventually radiated away as the asteroid rotates, and in the process it generates a tiny but measurable propulsive force which can influence the asteroid’s movement through space.

Bennu’s orbit around the Sun takes 1.2 years and brings it close to Earth every six years. To properly predict potential collisions with Earth, scientists need to know how the Yarkovsky effect influences that orbit.

Bennu is a carbonaceous member of the Apollo asteroid group – a collection of more than 8000 near-Earth asteroids with orbits that intersect Earth’s.

The asteroid was first detected on September 11, 1999 by the Lincoln Near-Earth Asteroid Research (LINEAR) project developed by NASA, the United States Air Force, and the Massachusetts Institute of Technology (MIT).

Bennu is thought to be composed of ancient carbonaceous material dating back to the formation of the solar system 4.6 billion years ago, and to pre-solar system material blown into space by dying stars known as red giants, and by supernovae – such as the one that triggered our solar system’s birth.

Earth-based observations indicate Bennu has a relatively smooth surface with a well-defined equatorial ridge line, and at least one prominent boulder – up to 20 metres wide – on its surface.

Scientists think the ridge line was created by fine-grained surface regolith particles accumulating in this area, due to the asteroid’s low gravity and rapid four-hour rotational period.

The OSIRIS-REx spacecraft (Origins, Spectral Interpretation, Resource Identification, and Security - Regolith Explorer) was launched on an Atlas V 411 rocket from the Cape Canaveral Air Force Base in Florida on September 8, 2016 on a seven-year mission to collect and bring home samples.

The probe will approach over the Pacific Ocean close to the equator before passing 16,000 kilometres over the city of Rockhampton in Queensland, Australia at 00:22 am AEST (10:22 am EDT, September 22) travelling south-southwest, reaching the skies over Adelaide in South Australia at 00:53 am local time, before zooming over the Great Southern Ocean and the Antarctic continent and heading back toward deep space.

While the best spots for watching are in Australia (and Antarctica), observers with telescopes will be able to see the craft from a much larger area. The website of the OSIRIS-REx mission has detailed instructions for how to spot it.

OSIRIS-REx will swoop through Earth’s skies on September 22 and 23, 2017.

NASA / OSIRIS-REX

The gravity-assist Earth flyby will give astronomers and sky watchers with high-end cameras a chance to view this rare encounter.

During the flyby manoeuvre Professor Phil Bland and colleagues from Curtin University will use the meteor-hunting Desert Fireball Network to develop a 3-D triangulated track of the spacecraft’s flight path to test the network’s capabilities.

Bland says teams equipped with high-end DSLR cameras will be stationed at key vantage points across the country, working together to track the flight path of OSIRIS-REx as it speeds over the continent.

The Desert Fireball Network project is designed to help NASA unlock the mysteries of the universe by studying meteorites, fireballs and their pre-Earth orbits.

Bland says together with NASA, the Desert Fireball Network is expanding to form a Global Fireball Observatory through the Solar System.

“We know very little about how the planets came together and why the Earth has the composition that it does,” says Bland.

“Projects like this will help fill in the gaps and provide a clearer picture of our origins.”

The gravity assist will fling the 2110-kilogram OSIRIS-REx spacecraft towards its August 2018 rendezvous with Bennu, and the start of its remote-sensing science mission.

OSIRIS-REx will study the asteroid in minute detail – analysing its chemical composition and mineralogy, characterizing its geologic and dynamic history, and mapping its surface to identify potential landing sites.

Eventually the spacecraft will slowly descend to the surface and use nitrogen gas to puff more than 60 grams of regolith into the sampler head fitted to the spacecraft’s robotic arm.